The present invention relates to a physical property measurement instrument which measures physical properties of an object nondestructively and without directly contacting the object.
As an instrument capable of ascertaining the physical properties of an object by nondestructive testing, there is, for example, the hardness measurement instrument disclosed in Japanese Patent Laid-Open Publication No. Hei 9-145691 by the present inventor. This hardness measurement instrument oscillates a contact element made to contact the surface of the object being tested and oscillates the contact element to easily and accurately measure the hardness of the object being tested according to an oscillation frequency of the contact element.
However, such a hardness measurement instruments has a problem that measurement is not possible when the contact element cannot be made to contact the surface of the test object because, for example, the object is covered with a material. In such situations, the conventional devices cannot measure the hardness or physical properties of the target object.
Even when the object is exposed, with a conventional device it is difficult to measure the hardness of the object when the contact element could not be contacted to the object under test because, for example, the target object is floating in water.
The noncontact physical property measurement instrument according to the present invention comprises a transmitting section which sends a wave to a test object in a medium; a receiving section which receives a wave reflected by the object; a self-excited oscillating circuit which connects the transmitting section and the receiving section to perform feedback oscillation; and a physical property measurement section which measures physical properties of the object according to an oscillation frequency of the self-excited oscillating circuit. Thus, differences in physical properties (e.g., hardness) of the object can be measured from the oscillation frequency of the self-excited oscillating circuit without directly contacting the contact element to the object to be tested. Therefore, even if the surface of the object is coated or it is otherwise not possible or difficult to directly contact the object, the physical properties of object can still be easily and accurately measured.
According to the present invention, the self-excited oscillating circuit may be provided with a gain change correction circuit which has a center frequency different from the center frequency of the self-excited oscillating circuit and increases gain in response to a change in frequency. When this is done, the sensitivity to the gain change due to the change in frequency can be enhanced, so that the physical properties of an object to be testedcan be measured more accurately.
According to the present invention, there may also be provided a storage section in which is prestored data on an interrelation between physical properties and the oscillation frequency of the self-excited oscillating circuit. Provision of such a storage section enables faster measurement of physical properties based on the value of oscillation frequency, without sacrificing accuracy.